1. Field of the Invention
This invention relates to electric circuits, and, in particular, to an optically isolated control circuit which allows continuous monitoring of the circuit being controlled to verify its proper operation.
2. Description of the Prior Art
In the design of many control systems it is frequently desirable to situate the object or device being controlled remotely from the control input signal. Furthermore, in many such installations, for example, nuclear power plants, it is desirable to completely isolate the control device from the control input. Although this has been achieved with prior art control systems, such control systems have typically been unable to monitor the correct operation of the device or object being controlled. For example, in prior art control systems, the control input signal has been supplied to a remotely situated object being controlled using optical or electronic techniques, but the station from which the control input signal was generated has been unable to detect the correct functioning of the remainder of the isolated control system.